One kind of article to which a lock of the invention has application is a clothes hanger which is arranged to carry clothing in such a manner that the clothing cannot be removed from the hanger unless the hanger is unlocked. This type of hanger is usually referred to as a security hanger. In the case of security hangers it is necessary to supply the hangers to clothing stores and the like in batches where a single key can unlock an entire batch of hangers. However, such a key must not be capable of being readily duplicated by a locksmith for if that were the case the purpose of the security hanger could be defeated. A conventional tumbler lock with a metal key is therefore not suitable for use on security hangers. It is an object of the invention to provide a lock and key combination which is of simple construction, is effective in use and which meets the abovementioned requirement.